“Scientists, former pilots and aviation pressure groups have accused the industry of knowing about the problem for decades and doing little to tackle it. But reports linking exposure to contaminated air with long-term harm to health have led to an increase in passengers and crew seeking redress, according to lawyers in the United States.”

Samples taken secretly from the planes of popular airlines have raised fresh concerns over passengers inhaling contaminated air.

Hundreds of incidents of contaminated air have been reported by British pilots Photo: GETTY

Fresh concerns about whether passengers could be inhaling contaminated air on aircraft have resurfaced, after undercover investigators claimed to have found high levels of a dangerous toxin on board several planes.

As part of an investigation by a German television network, ARD, and Schweizer Fernsehen (Swiss television), 31 swab samples were taken secretly last month from the aircraft cabins of popular airlines.

These were analysed in laboratories at the University of British Columbia, under the supervision of Prof Christian van Netten, a leading toxicologist.

Twenty-eight were found to contain high levels of tricresyl phosphate (TCP), an organophosphate contained in modern jet oil as an antiwear additive, which can lead to drowsiness, headaches, respiratory problems or neurological illnesses.

Scientists refer to the condition as Aerotoxic Syndrome. Dr Mackenzie Ross, a clinical neuropsychologist at University College London, says the illness may be affecting up to 200,000 passengers each year.